- Girisha, S.T. and Ragavendra, V.B., 2009. Accumulation of heavy metals in leafy vegetables grown in urban areas by using sewage water and its effect. Archives of Phytopathology and Plant Protection, 42(10): 956-959.

- Marinova, D., Ribarov, F. and Atanassova, M., 2005. Total phenolics and total flavonoids in Bulgarian fruits and vegetables. Journal of the University of Chemical Technology and Metallurgy, 40(3): 255-260.

- Moss, B., 1973. The influence of environmental factors on the distribution of freshwater algae: an experimental study: II. The role of pH and the carbon dioxide-bicarbonate system. The Journal of Ecology, 61: 157-177.